1. Field of the Invention
The present invention relates to a sound source locating system for locating the source of a noise and displaying the location of the source to cope with noises at a factory or the like.
2. Description of the Prior Art
At a factory or the like, many kinds of low-frequency noises having a frequency of 50 Hz to 60 Hz or a frequency double that frequency are generated from a power supply box and a transformer such as a relay. To cope with such noises, an operator measures a sound pressure distribution around a noise generating device with a noise meter to locate the source of the noise and take countermeasures against it. However, it is time-consuming and not efficient to locate the source. Then, a method of estimating the source of a sound such as a noise using an acoustic technique is now under study.
Conventionally proposed sound source locating methods include (1) one making use of the correlation between sound pressure waveforms and (2) one making use of acoustic holography. In the method (1), the property of a correlation function is utilized to estimate the location of a sound source from the correlation between sound waveforms collected at a plurality of locations whereas in the method (2), a basic wave is scanned in a space to be investigated, an interference sound generated by interference between the above basic wave and a noise is recorded for each scanning direction, and a sound pressure distribution in the space in which the basic wave has been scanned is reproduced from the obtained record to estimate the source of the noise.
Although measurement and analysis take long in the above method making use of the correlation between sound pressure waveforms and the above method making use of acoustic holography, the methods are effective in a limited space but have a problem that a system becomes large in size to improve accuracy when a sound source is located outside.
It is conceivable that a sound source is located using a directional microphone. Since most noises at a factory or the like are sounds having a low frequency range as described above, they have low directionability and even when a microphone is provided with directionability, it is difficult to locate a sound source.
In view of the above problems of the prior art, it is an object of the present invention to provide a sound source locating system which is simple in structure and can locate and display the source of a sound such as a noise at a factory or the like with high accuracy even when it is outside.